When was the last time you looked at a picture from your wedding day, or thought much about the promises you and your spouse made to each other so long ago (or not so long ago)?

One thing that may be easy to forget through the perfectly normal ups and downs of married life is that on your wedding day, you locked your heart.

You locked your heart when you chose your husband or wife to be your one and only, your best friend, your truest confidant, and your only lover. You locked your heart - with your spouse inside - and you committed to never allow anyone or anything to take priority over them. You committed to being fiercely loyal through thick and thin.

In a world that tells us that affairs are normal (and often celebrated), and that when one relationship gets stale it's time to find something new and exciting, remember that deep and fierce loyalty are at the foundation of a happy and healthy marriage. Remember that affairs - emotional or sexual - will never make you truly happy, especially in the long run.

On your wedding day you promised your spouse you would be completely loyal to him or her, and you locked your heart.

The best thing you can do to protect your marriage against an emotional or sexual affair is to keep your heart locked - with your spouse inside. When your heart is locked, there's no room for anyone else to take their place in any way, shape, or form. When your heart is locked, your conversations with members of the opposite sex are different. Your activities and time spent with members of the opposite sex are different. Your friendships with members of the opposite sex are limited and professional. Oh, and your eyes and thoughts are locked, too.
So, what does loyalty in marriage really look like? What does a locked heart look like?
What a Locked Heart Looks Like

Here are a few do's and don'ts of what a locked heart looks like (this list is by no means all-inclusive).

Note: While some of these may seem perfectly harmless, relationship experts have noted that casual friendships with members of the opposite sex can be a stepping stone in the path that leads to affairs. These experts have also pointed out that that path is often a more slippery slope than most people think. Because of this, it can be helpful for you and your spouse to evaluate from time to time, the friendships you have with members of the opposite sex (since everyone has interactions and friendships with members of the opposite sex).

Go on dates with friends of the opposite sex - whether to dinner, a movie, etc.

Go on trips with friends of the opposite sex.

Develop shared hobbies with friends of the opposite sex.

Text, call, or chat flirtatiously online with members of the opposite sex.

Flirt with members of the opposite sex (i.e. squeezing his or her shoulders, touching his knee, etc).

Do anything sexual with friends of the opposite sex.

Confide in your friends of the opposite sex.

Spend time alone with friends of the opposite sex.

Keep your friendships with members of the opposite sex a secret from your spouse.

​Let your eyes wander (aka, check others out).

Speak poorly about your spouse to others.

Mention out loud to your spouse or others how attractive someone of the opposite sex is.

View porn.

Check out pictures of friends (or strangers) of the opposite sex on social media.

What's the big deal with friends of the opposite sex?

Obviously, the idea of having a locked heart is that there isn't room for anyone else to even come close to playing the role or meeting the needs that only spouses should play and meet. In fact, there isn't really room for serious friendships of the opposite sex. At least, not in the way you may think.

I know, it's sounds a bit extreme, but one of the biggest culprits of affairs happens to be opposite-sex friendships. Innocent, seemingly platonic, friendships. Are you shocked? Don't be.

The subtle dangers of nurturing friendships with members of the opposite sex is exactly that - nurturing is happening. That effort and intentionality is being put into a friendship that should be put into marriage. Now, I'm not saying that you aren't going to have perfectly normal and appropriate interactions with co-workers and neighbors of the opposite sex. I'm talking about the potential danger of becoming "close" friends, even "best friends," with someone of the opposite sex (who isn't your spouse!). ​The danger comes when these "close" friends, especially those who don't live with you day-in and day-out, start to meet some of your deepest needs (especially if those needs are ones your spouse currently isn't meeting). Just think of your deep need to hear encouraging words and compliments. Or your deep need to have someone to share your favorite hobby with. Or your deep need to have someone tease you or make you laugh. Or your deep need to talk to someone who is actually interested in what you have to say.

It's all too easy to get caught in an emotional affair with a friend you spend time with at work, or in other settings, thinking this friendship is innocent because it's non-sexual. However, please be wary of those friendships with members of the opposite-sex, because they can very easily cross lines and lead to romantic thoughts, feelings, and actions, and damage your marriage in ways you will someday regret.

If you aren't sure about this potentially "extreme" view of limiting your friendships with members of the opposite sex, just read these 20 questions (and answer them honestly) to recognize the threat that opposite-sex friendships may pose to your marriage.

​In all that you do, remember that on your wedding day you promised your spouse you would be completely loyal to him or her, and that on your wedding day, you locked your heart.

Just keep your heart locked - with your spouse inside - and limit your friendships with members of the opposite sex (whether in person or online), in order to build the happy, healthy, well-nurtured marriage that you have always wanted. It will be well worth the effort. Guaranteed.